A LABORATORY GUIDE
FROM THE LIBRARY OF
WILLIAM A. SETCHELL,i864-i943
PROFESSOR OF BOTANY
MOf QT.Y r 1RRARV
WltUAM 4. SE7CHLL t
A LABORATORY GUIDE
G A GER
BY THE SAME AUTHOR
1 2 mo, xix + 640 Pages, 435 Illustrations. Flexible
Cloth, Round Corners, $1.50 Postpaid.
P. BLAKISTON'S SON & CO., PHILADELPHIA
A LABORATORY GUIDE
C. STUART GAGER
DIRECTOR OF THE BROOKLYN BOTANIC GARDEN
P. BLAKISTON'S SON & CO.
1012 WALNUT STREET
COPYRIGHT, 1916, BY P. BLAKISTON'S SON & Co.
THE MAPLE PRESS YORK. PA
This LABORATORY GUIDE is intended for the use of
students in their first course in universities and colleges,
or other institutions doing work of similar grade. It is
not a teacher's manual, and therefore does not include
information as to laboratory equipment, the purchase and
care of apparatus and materials, nor references to the
literature. The author believes that botanical instruc-
tion in America has now reached a stage where such
directions to university instructors is no longer necessary
As to the most desirable kind of laboratory directions
there is a wide diversity of opinion among teachers of ex-
perience. This GUIDE has been prepared in harmony
with the theory that the beginning student needs to learn,
in his first laboratory course, not merely botanical facts,
but how to observe and how to record his observations.
It is believed that rather full directions, such as are given
in the following pages, will accomplish this result. In
advanced courses the student should, of course, be ex-
pected to work with increasing independence, both in
his thinking and his handling of apparatus and material.
The GUIDE, substantially as here offered, has been used
with a number of large beginning classes.
The order of topics follows that in the author's Funda-
mentals of Botany, but with only minor changes the
GUIDE may be adapted for use with any text. -
The author is indebted to Dr. E. W. Olive for his care-
ful reading of portions of the page proof.
C. STUART GAGER.
BROOKLYN BOTANIC GARDEN,
October 14, 1916
To the Student I
ANATOMY AND PHYSIOLOGY
Meaning of the Terms . . . ,......*-.. 9
A Generalized Plant (Spirogyra) n
A Specialized Plant (e.g., The Bean Seedling) . ...... \ . 16
Structure of the Foliage Leaf . ............. \ . 17
Absorption of Water by Plants . ........;..... 29
The Path of Water in the Plant. . . . .. : . . . '. ( .- . . , . 34
Mechanical Uses of Water in the Plant ...,..."..... 36
Nutrition .- . . .... . ".' . 39
The Occurrence of Carbohydrates in Plants 40
Formation of Carbohydrates , . . ... . . . , . . .- ... 45
Alcoholic Fermentation 5
Respiration -.,...;.... 53
The Influence of External Conditions on the Plant 56
MORPHOLOGY AND LIFE HISTORY
Meaning of the Terms 59
An Outline of the Classification of Plants 61
Directions for Study 63
Polypodium vulgare (Common polypody) 63
Polytrichum commune (Common hair-cap moss) ....,. 74
Marchantia polymorpha (A liverwort) 84
Fucus vesiculosus (Bladder wrack) . . ,. . . . ... . . 96
Vaucheria sessilis (Green felt) . . . 102
Spirogyra (Pond scum, Green silk). 106
Pleurococcus vulgaris (Green slime) ' . IIQ
Phycomyces nitens (or Rhizopus nigricans) 113
Saprolegnia (Water mold) 117
Albugo Candida (Blister blight) 121
Agaricus campestris (Meadow mushroom) 125
Puccinia graminis (Wheat rust) I3 o
Isoetes (Quillwort) I34
Equisetum (Horsetail) I4 o
Lycopodium (Club-moss) I44
Selaginella (Little club-moss) I47
Zamia floridana (A cycad) !53
Pinus laricio (Austrian pine) ^i
Trillium (Wake-robin) I
A LABORATORY GUIDE FOR
TO THE STUDENT
THE NATURE AND PURPOSE OF LABORATORY WORK
A . The Laboratory:
1. The word laboratory is derived from the Latin word
labor, meaning work. A laboratory, therefore, is a
workshop. The essential part of laboratory work,
however, is not the manual but the intellectual.
Handling specimens, manipulating apparatus, tak-
ing notes, and making drawings, all are essential,
but are wholly secondary to thinking. A laboratory
exercise should be regarded always and primarily as
a thought exercise. Everything else that you do
with a specimen should be secondary to thinking
about it, and done only to aid thought.
2. The aim of laboratory work is to obtain facts at first
hand. Reading books on plants is only studying
about botany. To study botany one must have the
actual plants before him. It was Louis Agassiz
who said, " If you study nature in books when you
go out of doors you cannot find her." The posses-
sion of this first-hand knowledge makes the reading
of botanical books not only more easy, but vastly
more interesting. You can take more away from
the text because you bring more to it.
GUIDE FOR GENERAL BOTANY
3. Another aim of laboratory work, not less important
than the one just mentioned, is to acquire scientific
habits of thought and work; to learn the method by
which knowledge of the given science is acquired.
The scientific method differs from the unscientific
in laying emphasis upon the absolute necessity of
an orderly procedure in thinking and doing, upon
willingness to put aside prejudice and preconceived
notions, upon scrupulous neatness, accuracy of
thought and work, and careful attention to minute
details. The scientific method is not peculiar to
the natural sciences: it is just as essential in history
or language-study as elsewhere, and the highest
success in any intellectual pursuit is not possible
if the requirements of the scientific method are dis-
4. Observation is not merely looking at a thing. It
means looking for a purpose. The mental attitude
of the true observer is that of a questioner. The
great Swiss botanist, de Candolle, said, "The in-
terrogation point is the key to all the sciences."
Observation, then, consists in asking as definite
questions as possible about natural objects, and
seeking their answer, not from the instructor or
the text-book, but from the object itself.
5. Remember that your specimen is the final authority
in all matters of fact. Your first question should
never be, "What ought I to see?" "How many
parts ought the specimen to have?" but always,
without exception, "What do I see?" "How many
parts does the specimen have?" Possibly your
specimen may be found to differ from that of your
neighbor, or from the descriptions in the books.
TO THE STUDENT 3
If so, record that fact, and endeavor to ascertain
whether your specimen is abnormal, or whether
your observation of it is at fault in any way.
Always try to see all you can with the unaided eye
before resorting to the aid of a hand lens or microscope.
6. In mere observation one takes conditions as he finds
them; in experimentation, he determines, within
limits, the conditions under which the observation
is made. It is never possible to control, absolutely,
all the conditions in any experiment, but this is
partly compensated for by arranging side by side of
the experiment proper, a check or control. In the
experiment and control all conditions should be as
nearly alike as possible save one. The golden rule
in experimenting is: vary only one condition at a
time. Then if the experiment and control give
unlike results, we are justified in attributing the
difference to the unlike factor.
7. Before beginning an experiment, the object, or aim,
of the experiment must be clearly conceived and
clearly stated. The necessary materials and ap-
paratus should next be decided upon and procured.
Then may follow the operation, that is, the arrange-
ment of the materials and apparatus in a suitable
way. This step is frequently referred to as "set-
ting up" the experiment. The record of it should
include an accurate statement of the conditions at
the beginning of the experiment, together with
drawings of the apparatus and material as the
experiment is set up.
Next follows the observation, which must always be
made and recorded at the time and place of the experi-
ment. It should include suitable drawings. Fin-
4 A LABORATORY GUIDE FOR GENERAL BOTANY
ally, there may be stated the inference, that is, the
conclusion or conclusions which are thought to be
justified by the facts observed.
The record of an experiment, then, should follow
the outline given below:
2. Materials and apparatus (with drawings).
4. Observation (with drawings).
D. The Note-book:
8. The Note-book serves two purposes: First, the
making of it gives you opportunity to acquire
facility in describing what you observe. This is
not an easy accomplishment, but a very essential
one. "The greatest thing a human being ever does
in this world" said John Ruskin, "is to see something,
and tell what he saw in a plain way"
9. Secondly, the note-book serves as an index, to the
instructor, of what you have done and how well
you have done it. In addition to these two pur-
poses, the note-book will be a permanent record
for your own future use. It should contain a
complete record of all you observe, and the infer-
ences you make from these observations. It should
include written descriptions and drawings. In
both the latter the aim should be accuracy, neatness,
completeness, conciseness. Above all things, it
should be a record of your own observation, not
of your neighbor's. If, as may happen on rare
occasions, it becomes necessary to use your neigh-
bor's notes, always state the fact clearly and frankly
in your own book.
TO THE STUDENT 5
10. In writing your notes, the aim should be to give
such a clear account of what you have seen and done
that anyone else who knew nothing of the subject
could profit by reading them. In other words,
aim to make your notes usable in the future. Your
text-book may be regarded in one sense, as the
author's laboratory note-book. Seek to make
your laboratory note-book an accurate and readable
illustrated text on the ground covered by your
E. Laboratory Drawings:
11. Drawing is one of the greatest aids to observation.
This is its main purpose in the laboratory. It
is often said that "persons who cannot draw cannot
see." This is probably an extreme statement,
but it is undoubtedly true that one who can make
an accurate drawing of a thing has observed it
more accurately than one who cannot.
12. Laboratory drawings should aim to represent the
thing only as it is, not as it may impress one at
first sight. They differ in this respect from the
work of the artist. For example, to show the
exact number and location of the veins of a leaf
would ruin the artist's picture; but without those
details the laboratory drawing would be of little
13. As directed in the GUIDE, make as thorough an
observation of the object as possible before you
begin to draw; then make the drawing.
14. Unless otherwise directed, make' outline drawings,
shading only where absolutely necessary. In
general, every line in your drawing should represent
some fact of structure in the specimen.
15. Be sure to make the drawing large enough so that
A LABORATORY GUIDE FOR GENERAL BOTANY
all details may be included without crowding or
1 6. First sketch in the outline lightly with a 5H drawing
pencil. In finishing a 2H pencil may sometimes be
17. All drawings should be on unruled sheets, and only
on one side of the sheet. They should be labeled
and numbered consecutively throughout the course
by writing under each the abbreviation Fig.,
followed by the proper numerals, and then by the
legend or label, stating what the object is, and what
view of it is shown, as for example, " Cross-section,
end view." Each drawing should have all of its
essential parts labeled by extending straight
horizontal dotted lines from the various parts
(using a ruler), and writing the name of the part
at the end of the line. ,
1 8. The arrangement of the drawings on the page
should receive careful attention, so as to make as
attractive and well balanced a page as possible.
Crowding should be avoided, and on any one page
should be included only those drawings that repre-
sent parts of the same plant, or pertain to the
19. The various pages of drawings should be numbered
and labeled near the top of the page at the middle
thus; Plate I. Throughout your written notes,
when describing a structure or apparatus, repre-
sented by a drawing, refer to the drawing by its
proper number and the number of the Plate (e.g.,
Plate IV, Fig. 5).
20. At the completion of the course, arrange a "Table
of Contents," listing the main topics, as indicated
in the LABORATORY OUTLINE, in the order in which
TO THE STUDENT 7
they occur in the note-book, with the page number
near the right-hand edge, and a neat dotted line
extending from the subject to the page number.
F. The Microscope:
21. Full directions for the use and care of the compound
microscope will be giver/ by the instructor. The
student should clearly realize from the first that the
science does not reside in the instrument. The latter
is merely an aid to the eyes, but not to the mind,
and is made necessary by the limited range of our
unaided vision. It should be used only after one has
seen all that he possibly can with the unaided eye.
22.. The following points should be constantly borne
in mind :
(a) Keep all parts of the instrument, especially
the lenses, scrupulously clean.
(b) Never attempt to take the instrument apart.
(c) Never remove lenses from the stand. If it
is ever absolutely necessary to do so, then
(d) Never lay a lens down on the table.
(e) Never touch the lens with the fingers or eyelids.
(/) Never try to clean the lens with the handkerchief
or anything except lens paper,
(g) Never examine any object without covering
it with a cover-glass.
(ti) Never allow the objective to touch the cover-
(i) Never focus down while looking through the
(k) Be sure that the slides and covers are absolutely
clean. Dirt will be magnified as well as the
object you are studying.
(0 Handle all slides and cover-glasses by the edge,
never touching their surface with the fingers.
A LABORATORY GUIDE FOR GENERAL BOTANY
(m) Don't shut one eye when looking through
the instrument. Ability to work with both
eyes open is easily acquired, is much less
tiring, and is an advantage in many ways.
(n) Never use high powers when low powers will serve.
(o) Examine all objects with the low power first,
then with the high power, if necessary.
(p) Never set the instrument away with a micro-
scopic slide under the objective, nor with the
high-power objective over the aperture.
(q) When the laboratory period is over, remove
the preparation you have been studying, and
leave the microscope with the low-power
objective over the aperture.
ANATOMY AND PHYSIOLOGY
I. MEANING OF THE TERMS
A. Plant physiology is that branch of botany which deals
with the vital activities of plants. But physiological
processes or functions are carried on by various parts
of the plant, and these parts all have their own char-
acteristic structure. In order to understand the proc-
esses we must know the internal as well as the
external structure of the parts concerned. This knowl-
edge requires dissection, and this phase of the science
is, therefore, called anatomy. Microscopic anatomy is
called histology. Just as the processes cannot be
intelligently considered apart from the structures
involved, so, also, the study of anatomy apart from
physiology is meaningless.
B. In the lowest (i.e., most simply organized) plants all
functions, both nutritive and reproductive, are per-
formed by every structural unit or cell; but in more
highly organized plants there are special parts or
organs for the performance of each function; for ex-
ample, roots to take in moisture, flowers to form seed.
In other words, in the higher plants there is a division
of physiological labor, or, as it is sometimes called, a
physiological division of labor. While not entirely
wanting, the division of physiological labor is less
marked in the lowest plants.
10 ANATOMY AND PHYSIOLOGY
Because they are composed of organs, plants and
animals are termed organisms.
C. Thus we see that some plants have a generalized plant-
body, others a more highly specialized one. To under-
stand the various life-processes carried on by plants,
we must have a knowledge of their structure. A gen-
eralized plant will be studied first, then the structure
of a higher (i.e., more highly specialized) plant. This
will be followed by an elementary study of the funda-
mental life-processes involved in the nutrition and
growth of the individual. The second part of the
course will be devoted to studying the various kinds
of plants, and the numerous ways in which different
kinds of plants solve these same life-problems of nutri-
tion and reproduction.
II. A GENERALIZED PLANT (Spirogyra)
A. Naked-eye Characters:
1. Carefully take a small bit of this plant between the
thumb and fingers and note its "feel." Suggest
why it is sometimes referred to as "green silk."
2. Carefully lift up some of the material with a needle,
and describe the form of the plant. How many
centimeters long are the longest filaments you can
3. Can you detect any evidences of a differentiation
of the plant into shoot (i.e., stem and leaves) and
B. Microscopic Characters:
i. The plant as a whole.
(a) Mount two or three filaments in water.
(b) Note that the filament is composed of separate
structural units, placed end to end. These
units are cells.
(c) Are the filaments more than one cell thick?
Do they branch? Are they of uniform diame-
ter? Compare the length of the various cells
with each other. Compare the shape of the
end cell with that of the others. What is the
shape of the filament as seen in imaginary cross-
section? Very careful focussing is necessary in
order to answer this question correctly.
(d) Accurately measure the length (in millimeters)
of a piece of filament lying straight under the
cover-glass, then count the number of cells in
12 ANATOMY AND PHYSIOLOGY
this piece. Calculate the average length of the
cells, and the number of cells in the longest
filament observed. Estimate the length of an
individual cell in terms of its diameter, and from
this calculate the diameter of the filament.
(e) Using the low power and removing the cover-
glass, carefully cut a filament apart with the
scalpel, causing as little injury as possible. As
you do this observe the exposed end-walls of
the uninjured cells that now terminate the fila-
ment where it was broken apart. Describe and
try to account for what you see. Is there any
evidence of the existence of a force within the
cell? If so, in what direction does it act?
Make two outline drawings, showing the con-
ditions before and after cutting.
(/) Make a diagram about 75 mm. long, illustrating
the outline of the three terminal cells of a fila-
ment, as seen in optical section. Omit all de-
tails of cell-structure.
2. The individual cell.
(a) Center your attention on any one of these cells,
and identify the following organs of the cell :
(1) A cell-wall, enclosing all other parts of the
cell. Is it transparent or not? Give a
reason for your answer. Note its relative
thickness. The wall is composed of cellu-
lose. Has each cell its own end -wall, or is
there a common end-wall for two adjacent
(2) The substance enclosed by the cell-wall is
largely living matter, or matter in the living
state. It is called protoplasm. The unit
of protoplasm of each individual cell is
A GENERALIZED PLANT 13
called a protoplast. Distinguish the follow-
ing parts of a protoplast:
(3) The prominent green chlorophyll-band, or
chromatophore. Describe its form, the
number of turns it makes in the cell, and
the outline of its margin. Infer its shape
in cross-section. How many in each cell?
If more than one, do they coil in the same
direction? Can you detect free ends of the
chromatophore? Are they continuous from
cell to cell? The color of the chlorophyll-
band is due to the presence of a green pig-
(4) The denser areas within the chromatophore
are regions of starch-formation. In the
center of this area is the starch-forming
body, or pyrenoid. Surrounding the pyre-
noid are starch grains.
(5) Make a detailed drawing, 10 mm. wide and
15 mm. long, showing the details of struc-
ture of a portion of the chlorophyll-band,
as seen under high power. Indicate on the
drawing the names of all parts shown.
(6) At or near the center of the cell find a dense,
colorless body, the nucleus, surrounded by
a less dense layer of colorless cytoplasm.
Describe the shape of the nucleus. From
the layer of cytoplasm trace
(7) Delicate cytoplasmic strands, extending to
the pyrenoids, and to
(8) The lining layer of cytoplasm. This layer
(sometimes called " primordial utricle ") is
in intimate contact with the entire inner
surface of the cell-wall, and is difficult to
14 ANATOMY AND PHYSIOLOGY
identify. Its two surfaces are plasma
(9) The clear spaces in the cell are vacuoles,
filled with cell-sap.
(10) Make a drawing of a cell at least 10 cm. in
( 1 1) The lining layer may be easily demonstrated
as follows: Place a drop of a 5 per cent,
solution of common salt (sodium chloride)
at one edge of the cover-glass. Be careful
that none of the solution runs over onto the
cover-glass. By placing a small piece of
blotting paper at the opposite edge of the
cover-glass, the water will be removed, and
the salt solution drawn under the cover-
glass, irrigating the specimen. Follow with
another drop if necessary. Observation
should be continuous while the specimen
is being irrigated with the solution.
(12) Describe the effect of the salt solution on
the lining layer.
(13) Loosening the lining layer, as above, is
| termed plasmolysis (i.e. , loosening the plasm) .
The cell is said to be plasmoly zed.
(14) Make a drawing, the same size as the pre-
ceding, showing a plasmolyzed cell.
(15) Before plasmolysis the lining layer was held
close against the cell-wall with a force,
already detected (e, p. 12), sufficient to
cause a rigid condition of the cell called
turgor or turgidity.
(16) Now replace the salt solution with fresh
tap-water, by the method described in (n)
above. Describe the effect on the cell.
What condition has been restored?
A GENERALIZED PLANT 1$
3. Make a diagram, at least 25 mm. in diameter, show-
ing the appearance of a cell in imaginary cross-
section taken through the nucleus.
4. Do you think Spirogyra is a unicellular or a multi-
cellular plant? If the latter, how many cells con-
stitute one plant? Give reasons for your opinion
NOTE. If time permits, the study of cell-structure may be ex-
tended by observing the cells in young leaves of Elodea, the skin
(epidermis) of onion scales, the basal cell of the hairs on any seed-
ling cucurbit, or the cells of the stamen hairs of Tradescantia.
III. A SPECIALIZED PLANT (e.g., The Bean Seedling) 1
A . The plant as a whole:
1. Examine the seedling given you and note that it is
composed of an aids with appendages; the axis, of
root and shoot; the root, of a primary root with
branches (secondary roots); and the shoot, of a
main stem, bearing leaves. Has the main stem
branches? Is this true of all plants? What is the
difference between a stem and a branch?
2. Describe fully the location of the leaves and their
attitude on the stem. Do they occur on both the
^main stem and its branches? The places on the
fstem where leaves grow are nodes. The spaces
between the nodes (vertically) are called internodes.
3. Compare the size of the upper with that of the lower
Bangle made by the leaves with the stem. This
Jupper angle is called the leaf-axil (Latin axilla,
4. Do you find any structures in the leaf-axils? If so,
^describe them. What are they?
5. With what do the tips of the main stem and branches
6. Describe any other outgrowths of stem or branches.
7. Make a drawing of the plant as large as your draw-